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Biomedical subjects

A K Slob

Publications and source records attributed to A K Slob.

At least 91 records · Page 5Linked to original sources
PubMed1988

Vaginal bacterial flora partially determines sexual attractivity of female rats.

This study shows that the bacterial flora of the rat's vagina plays a role in the determination of female sexual attractivity. In the experiment described, the change in attractivity of a female rat was monitored during the estrous cycle by using a residential plus-maze. The time that male rats spent in the vicinity of a female rat was used as a measure of the attractivity of that female. The vaginal bacterial flora of one of these females was killed by daily injection in the vagina of an antibiotic solution. It was found that male rats preferred the company of an estrous female with an untreated vagina over the company of an estrous female with a 'sterilized' vagina. This indicates that the vagina produces an olfactory signal which plays a role in her attractivity for a male rat.

Animals↗
PubMed1988

Mutually gratifying heterosexual relationship with micropenis of husband.

Three adult patients with micropenis are described: two genetic females, reared as boys, with congenital adrenocortical hyperplasia (CAH), and one male with anorchia. The patients had a male gender identity/role. All three had established a satisfying heterosexual relationship. For only one of the patients intravaginal intercourse was possible. In one patient (with CAH), penile reconstructive surgery was attempted but failed. Nevertheless, he developed a satisfactory sexual relationship with a woman friend. This report illustrates that for patients with micropenis, penile reconstructive surgery is not obligatory for the establishment of a satisfying sexual relationship.

Adrenal Hyperplasia, Congenital↗
PubMed1988

Immediate postnatal rise in whole body androgen content in male rats: correlation with increased testicular content and reduced body clearance of testosterone.

Whole body content of androgen (testosterone + 5 alpha-dihydrotestosterone) was invariably higher in male than in female rat pups killed 1 or 3 h after natural delivery, whereas androgen content was equivalent in males and females killed immediately or 6, 12, and 24 h after birth. Testicular content of androgen was significantly elevated in males killed 1 and 24 h after birth, compared with levels in males killed immediately, or 3, 6, and 12 h after birth. Thus, heightened testicular androgen content was only initially associated with increased systemic levels of androgen in males during the immediate postpartum period. A second study assessed the possibility that the body's clearance (i.e., metabolism plus excretion) of testosterone is lower in newborn rats upon separation from the placental circulation than in slightly older pups. Rats of both sexes killed 1 and 3 h after s.c. injection of [3H] testosterone had significantly higher plasma concentrations of [3H] testosterone as well as several 5 alpha-reduced androgens (5 alpha-dihydrotestosterone, 3 alpha-androstanediol, and androsterone) when injections were given within minutes as opposed to 24 h after birth. This suggests that in both sexes the clearance of testosterone is slower immediately after birth than at later ages. This phenomenon together with a brief postnatal elevation in the testicular synthesis and secretion of testosterone may explain the temporary rise in circulating androgen concentrations that occurs in the newborn male rat.

Age Factors↗
PubMed1987

Testosterone, testis size, seasonality, and behavior in group-living stumptail macaques (Macaca arctoides).

During a 28-month period, data were collected on physiological parameters and sociosexual behavior of 13 adult male members of a large mixed-sex group of stumptail macaques living in an outdoor cage. Monthly measurements of plasma testosterone, testis size, and body weight revealed no systematic seasonality. Seasonal variations did occur in branch shaking and grooming (both with low rates in winter), but not in other behaviors studied (copulation, masturbation, aggression). Dominance ranks were stable throughout the study period and were not significantly correlated with mean testosterone levels. Temporal fluctuations in behavioral frequencies did not parallel testosterone fluctuations. Interindividual differences in behavioral frequencies were often correlated with dominance rank, but not with testosterone levels.

Aggression↗
PubMed1987

Physiological aspects of puberty in group-living stumptail monkeys (Macaca arctoides).

Physiological changes around the time of puberty were studied in a longitudinal manner in male and female stumptail macaques. In the male, testicular descent (mean age 3.3 years) is an early sign of puberty, which coincides with onset of the pubertal spurt in body weight and testis growth and precedes the pubertal rise in plasma testosterone. In the female no clear external signs of puberty have been found. Measurements of plasma progesterone yielded proof of first ovulation (mean age 3.7 years), a late sign of puberty in primates. This event coincided with a fall in the rate of body weight growth at the end of the pubertal growth spurt. Reproductive capacity of both males (first ejaculation) and females (first conception) appears to be reached around the 4th birthday.

Animals↗
PubMed1987

Attractivity of male rats induced by estradiol and progesterone.

From the present study it appears that castrated male rats can be made attractive to intact males by estradiol benzoate plus progesterone (EB + P). For the determination of attractivity a residential plus-maze was used in which the resident male could choose between the company of the experimental male and that of an ovariectomized female with or without EB + P. In one experiment the males were castrated in adulthood; these animals were less attractive than the ovariectomized females with a similar hormone treatment. In a second experiment it was found that males that had been castrated at birth were as attractive as the ovariectomized females, after treatment with EB + P. These findings indicate that the attractivity that can be induced by EP + P in gonadectomized adult rats is somewhat but not wholly reduced if androgen is present during the neonatal period.

Animals↗
PubMed1987

Homosexual and heterosexual partner preference in ovariectomized female rats: effects of testosterone, estradiol and mating experience.

Ovariectomized female rats, longterm treated with estradiol benzoate (EB, 20 micrograms, 3 x/week) or testosterone propionate (TP, 0.4 mg, 3 X/week), were tested for homo- or heterosexual partner preference behavior with either tethered animals (sexually active male vs. estrous female) or animals behind a wire mesh. A preference score was calculated by subtracting the time spent in the vicinity of the stimulus female from the time spent in the vicinity of the stimulus male. Thus, a positive score indicates preference for the male (heterosexual preference), a negative score preference for the female (homosexual preference). Two weeks of EB treatment caused a clearcut preference for the male incentive. This heterosexual preference was significantly different from the indistinct preference of the TP-treated females. Sexual interaction with a freely moving active male (with or without a vaginal mask which prevented intromissions) did not alter the preference for the male of the EB-treated females. It did affect, however, the preference behavior of the TP-treated females significantly: it changed in the direction of the sexually active estrous incentive female, i.e., a homosexual preference. This change in preference could not be attributed to the experience of penile intromissions, it occurred despite the presence of a vaginal mask. Apparently, being mounted by a sexually active male had a negative reinforcing value in the TP-treated female rats and provoked a homosexual partner preference.

Animals↗
PubMed1986

Heterosexual experience and isosexual behavior in laboratory-housed male stump-tailed macaques (M. arctoides).

Three feral-born male stump-tailed macaques were housed together for 9 years from prepubertal age. The animals were then transferred to another laboratory and housed individually. They were pair-tested with each other (isosexual tests) and with females (heterosexual tests) for the first time in their adult lives. The study revealed that these males preferred females as sexual partners. They preferred each other as groom partner. The heterosexual experience did not drastically alter sociosexual behavior between the males.

Animals↗
PubMed1986

Castration, sex steroids, and heterosexual behavior in adult male laboratory-housed stumptailed macaques (Macaca arctoides).

The sociosexual behaviors of six stable male-female pairs of stumptailed monkeys were studied in half-hour pair tests. Their performance before and after castration of the males was compared. The effects of replacement therapy with sex steroids on male-female interaction were studied. Also the effects of new females as sexual partners were investigated. Castration caused a significant decrease in sexual behavior. Individual males could display ejaculatory behavior up to about 1 year postcastration. Dihydrotestosterone propionate (75 mg/week/male) alone or in combination with estradiol benzoate (0.9 or 3 mg/week/male) was not effective in restoring sexual behavior to precastration levels in the three castrated males tested. Replacement therapy with testosterone propionate (75 or 10 mg/week/male) was effective in restoring copulatory behavior in half of the castrated males. In some males the introduction of a new female caused an increase in sexual activity, usually when sexual activity with their familiar partner was low. This occurred both in the castration condition and in the steroid treatment period, suggesting, that low activity was caused by low "motivation" and not by the inability to perform.

Androgens↗
PubMed1986

Physiological changes during copulation in male and female stumptail macaques (Macaca arctoides).

Radiotelemetric recordings were made of uterine contractions in female stumptail macaques, and of heart and respiratory rate in stumptail monkeys of both sexes, before, during and after copulation. These data were fed into a multichannel recorder, along with a spoken record of behavioral changes. Males' heart and respiratory rates were raised during penile thrusting, reached a peak and then fell sharply after ejaculation. Uterine movements were similar during successive copulations. After uterine movements associated with penile thrusting prior to ejaculation a rise in contraction force occurred which lasted about 15 seconds. It is in this period, if ever, that a climax face was displayed by the female. The female's look-back and reach-back behaviors were not linked to either the pattern of uterine contractions or the occurrence of the climax face.

Animals↗
PubMed1986

Ontogeny of sex differences in open-field ambulation in the rat.

The effects of age and gonads were studied in rats subjected to open-field tests, during which ambulation behavior was recorded. Subjects were three groups of male and female rats: sham-operation on day 1 and day 21; gonadectomy on day 1 and sham-operation on day 21; and sham-operation on day 1 and gonadectomy on day 21. Half of each group were tested in a circular open field (3 min/day, 3 consecutive days) on days 28-30; the others were tested on days 47-49. Representatives of both batches were tested again in a square open field on days 76-78. There was a sex difference in ambulation at 77 days, but not at earlier ages. In animals gonadectomized on day 1 or day 21 the sex difference in adulthood failed to occur, because castration caused the males to ambulate as much as sham-operated and ovariectomized females. On the basis of our results and reports in the literature it is suggested that testicular secretions around puberty have an organizing effect on ambulation behavior. The intact adult male rat ambulates less than the adult female and this difference persists after castration in adulthood. Castration well before puberty prevents the development of the adult sex difference.

Aging↗
PubMed1986

Sexual behaviour during ovarian cycles, pregnancy and lactation in group-living stumptail macaques (Macaca arctoides).

Sexual interactions were studied in a large, well-integrated group of stumptail macaques, continuously living together. Copulations with the highest-ranking male and with young males were equally distributed over the ovarian cycle. Copulations with other adults males also occurred during all cycle phases, but were most frequent peri-ovulatory. This was most distinct in conceptive cycles. Copulatory activity continued during early pregnancy, but was virtually absent during the middle and latter part of pregnancy and during lactation. Fluctuations in copulation frequency could be attributed to fluctuations in female attractivity (as measured by directed male masturbations), but not in proceptivity (spontaneous presents) or receptivity (acceptance ratios). However, hormonal influences on attractivity could be overruled by social factors. With regard to the expression of heterosexual behaviour, stumptail macaques seem to be less hormone-dependent than other primate species studied, both in the laboratory and under more natural circumstances.

Animals↗
PubMed1985

Food conditioning, castration, testosterone administration and sexual behavior in the male rat.

Chronically food-deprived male rats, when paired with a female rat in heat, were rewarded by receiving a food pellet following each intromission. Following castration there was a rapid decline in all aspects of male sexual behavior: after 3 weeks all sex behavior had stopped. There were no differences between the conditioned males and their yoked controls. Substitution with two doses of testosterone (through silastic implants) restored sexual behavior, but equally so in the conditioned and the control animals. Removal of the testosterone implant again caused a very rapid decline in sexual behavior, no differences between experimental and yoked control males. These results suggest that food, as a non-sexual stimulus, does not cause hungry male rats to continue to copulate for prolonged periods following castration. Furthermore, the combination of chronic food deprivation plus castration do summate with each other in the very rapid decline and cessation of male sexual performance.

Animals↗
PubMed1985

Social factors and puberty in female rats.

The effects of postweaning social conditions on the age of puberty were studied in female rats from an early- and a late-maturing strain. The postweaning living conditions consisted of the presence or absence of an adult rat (intact or gonadectomized male, or intact female), or of bedding soiled by adult males. The infantile females exposed to these conditions were caged either singly or with three peers. Puberty was studied in terms of first ovulation, verified always by ovarian histology. Females of the late-maturing strain living without peers reached puberty about 2 days earlier than females that grew up in groups of four, irrespective of the presence or absence of an adult animal. In neither strain was puberty accelerated by the presence of intact males or the soiled bedding of such males. These results do not support the view that in the rat pheromones from adult males enhance puberty in females, contrary to what is known to happen in the mouse.

Animals↗
PubMed1983

Anterior hypothalamic lesions and pubertal development in female rhesus monkeys.

Electrolytic lesions were made in the anterior hypothalamus of 8 prepubertal female rhesus monkeys, aged 1.1-1.7 years. Six unoperated females served as controls. No effects were found of the lesions upon age and body weight at menarche or at first ovulation, as estimated by blood levels of progesterone and laparoscopic observations. From these findings it appears that the neural control of puberty in the female rhesus may not be exerted through the anterior hypothalamus, in contrast with the rat and ferret. Further, an attempt was made to identify biometric correlates of hormonal changes during puberty. Firstly, the well known dip in growth rate, about 0.4 years before menarche, was observed. Secondly, there was a marked spurt in growth of the nipples starting at 0.2 years before menarche. The close temporal association between accelerated nipple growth and menarche suggests that both of these developmental characteristics result from changes in (presumably ovarian) steroid hormone secretion.

Age Factors↗
PubMed1983

Prenatal testosterone propionate and postnatal ovarian activity in the rat.

Testosterone propionate (TP) was given to rats on days 16 through 20 of pregnancy (2 mg/day). Female young had masculinized external genitalia. Sexual maturity was accelerated in TP females, despite lower weights and shorter lengths of body and tail. Placental and body weights were lower in TP females and males than in controls. The inhibiting effect of TP on postnatal growth is probably mediated by its effect on birth weight through placental damage. Ovarian cyclicity occurred upon reaching sexual maturity. In one experiment TP females were ovariectomized at 6 weeks, and given ovarian and vaginal grafts. Most of these animals showed regular cyclicity in vaginal smears between 74-100 days. Thus neither the 'early', nor the 'delayed early androgen syndrome' occurred in these experiments. This absence of effect of prenatal TP on ovarian cyclicity is attributable to a placental barrier for testosterone. When maternal plasma testosterone was raised 20-fold by exogenous TP, foetal testosterone levels remained unchanged. More detailed information was obtained when labelled testosterone was infused into a pregnant rat. Testosterone did not reach the foetus as such, but mainly as androsterone, which cannot be converted into oestrogens. This explains why prenatal TP can cause masculinization of genitalia, without 'masculinizing' the gonadotrophin secretion pattern in female rats. The latter process would presumably require oestrogenic compounds.

Animals↗